Avalanche Forecast

Issued: Jan 7th, 2019 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Deep Persistent Slabs and Storm Slabs.

ian jackson, Parks Canada

Banff Yoho Kootenay.

Natural activity has tapered, but any slope that hasn't avalanched is primed for human triggering. More avalanche control using explosives today triggered avalanches with every bomb and up to size 3.5!

Summary

Weather Forecast

Tuesday looks to be cold, partly cloudy and dry and then we will see warmer temperatures and some light precipitation starting Wednesday and into Thursday. Only 5- 15 cm is expected by end of day Thursday. Winds will be moderate SW increasing to strong on Thursday.

Snowpack Summary

Up to 70 cm of recent snow with variable wind effect has put a dense load over the persistent weak layers. In thicker snow pack areas, the Dec. 10th weak layer of facets is now down 100-150cm with a stronger snowpack below. In thin snowpack areas, the Dec.10th layer is mixed in with the basal facets and October crust.

Avalanche Summary

The natural avalanche cycle has tapered off, but conditions are still primed for human triggering. Avalanche control using explosives today on the Icefields Parkway and Mt Dennis in Yoho produced results up to size 3.5 with every shot producing a large avalanche. Some avalanches were triggered with just the force of the bag hitting the slope.

Confidence

Due to the number and quality of field observations

Problems

Deep Persistent Slabs

More avalanche control work today proved that this layer is still touchy. Most avalanches scrubbed down to the October 26th facet crust or the ground. This layer needs time to adjust to the load and this problem will be around for some time.

Be aware of the potential for wide propagations which could result in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3.5

Storm Slabs

These storm slabs exist in many areas and should be treated with caution in avalanche terrain, but should only be a problem in the short term. Expect it to last for a couple more days. If you trigger this layer, watch for the step down avalanche

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 3

Valid until: Jan 8th, 2019 4:00PM